System and method for thermal gradient control in thin shell structures
Described herein are devices and methods for reducing thermal stresses in a rotating, foraminous thin-shelled roll for drying permeable and semi-permeable webs by blocking axial flow of heated air through an axial channel formed between two corrugated layers in the shell. The axial channels extend between spaced-apart, parallel end members each having an inner face, and a plurality of alternating straight thin divider strips and bent thin strips extending axially between and evenly-spaced around the circumference of the inner faces of the end members to form an annular cylinder with radial channels therethrough. Affixing at least one impermeable insert into a radial channel so that it extends through the radial channel and across at least a portion of the faces of the two tiers of bent strips blocks the axial channel therebetween and prevents the passage of air therethrough to the end member.
1. A rotating, foraminous thin shelled roll for drying permeable and semi-permeable webs comprising:
a) a pair of spaced apart, parallel end members, each having an inner face,
b) a plurality of alternating straight thin divider strips and bent thin strips extending axially between and evenly-spaced in a circle around the inner faces of the end members to form an annular cylinder having a longitudinal axis, wherein:
i. the bent strips define radial channels along the length of the adjacent divider strips for receiving air therethrough, thereby providing the foraminous characteristic of the thin shelled roll,
ii. the foraminous wall of the cylinder comprises two tiers of bent strips disposed between the straight strips, and
iii. an axial channel extends concentrically along the longitudinal axis between the two tiers of bents strips from one end member to the other;
c) at least one impervious thin strip disposed about the surface of the annular cylinder and aligned at one fixed edge with an end member, thereby reducing the width of the foraminous area of the thin shelled roll; and
d) at least one impermeable insert aligned at and/or near the free edge of the impervious strip and extending through a radial channel and across the entire axial channel and at least a portion of the faces of the two tiers of bent strips so as to block the axial channel therebetween completely and prevent the passage of air therethrough to the end member.
2. The thin shelled roll of claim 1 , further comprising at least one impermeable insert disposed in every radial channel around the circumference of the cylinder that is aligned at or near the free edge of the impervious strip.
3. The thin shelled roll of claim 1 wherein the impermeable insert is a steel plate affixed to the parallel faces of the two tiers of bent strips.
4. The thin shelled roll of claim 1 wherein the impermeable insert is cast into the radially oriented channels formed by the corrugations aligned at and/or near the edge of the impervious strip.
5. The thin shelled roll of claim 1 wherein each end member is manufactured from a material having a first coefficient of thermal expansion.
6. The thin shelled roll of claim 5 wherein the at least two dividers are manufactured from a material having a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.
7. The thin shelled roll of claim 5 wherein the at least two dividers are manufactured from a material having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion.
8. A method of manufacturing a rotating, foraminous thin shelled roll for drying permeable and semi-permeable webs comprising:
a) providing a pair of spaced apart, parallel end members, each having an inner face,
b) providing a plurality of alternating straight thin divider strips and bent thin strips extending axially between and evenly-spaced in a circle around the inner faces of the end members to form an annular cylinder having a longitudinal axis, wherein:
i. the bent strips define radial channels along the length of the adjacent divider strips for receiving air therethrough, thereby providing the foraminous characteristic of the thin shelled roll,
ii. the foraminous wall of the cylinder comprises two tiers of bent strips disposed between the straight strips, and
iii. an axial channel extends concentrically along the longitudinal axis between the two tiers of bents strips from one end member to the other;
c) providing at least one impervious thin strip disposed about the surface of the annular cylinder and aligned at one fixed edge with an end member, thereby reducing the width of the foraminous area of the thin shelled roll; and
d) affixing at least one impermeable insert aligned at and/or near the free edge of impervious strip and extending through a radial channel and across the entire axial channel and at least a portion of the faces of the two tiers of bent strips so as to block the axial channel therebetween completely and prevent the passage of air therethrough to the end member.
9. The method of claim 8 further comprising affixing at least one impermeable insert at every radial channel around the circumference of the cylinder that is aligned at or near the free edge of the impervious strip.
10. The method of claim 8 wherein the impermeable insert is a steel plate affixed to the parallel faces of the two tiers of bent strips.
11. The method of claim 8 wherein the impermeable insert is cast into the radially oriented channels formed by the corrugations aligned at and/or near the edge of the impervious strip.
12. The method of claim 8 wherein each end member is manufactured from a material having a first coefficient of thermal expansion.
13. The method of claim 12 wherein the at least two dividers are manufactured from a material having a second coefficient of thermal expansion that is greater than the first coefficient of thermal expansion.